These studies are designed to analyze the effects of oncogene expression on cell growth and differentiation. We have previously shown that inducible antisense c-fos constructs can inhibit fibroblast growth, and that single stranded antisense oligomers can induce differentiation of HL-60 cells. Antisense c-myc constructs only mildly inhibit fibroblast growth, possibly because of an inability to obtain a suitable ratio of antisense:sense RNA. A more useful model system is the 32-D cell line, in which removal of interleukin-3 from the media induces a fall in c-myc and growth arrest; conversely, addition back of Il-3 induces a rise in c-myc with a subsequent re-entry into the cell cycle. Induction of antisense c-myc RNA during Il-3 induced quiescence should allow more detailed study of the role of c-myc in the cell cycle.